Abundance, Sizes, and Major Element Compositions of Components in CR and LL Chondrites: Formation from Single Reservoirs

TL;DR

This study analyzes the composition and sizes of components in CR and LL chondrites, supporting single-reservoir models for their formation and providing insights into their chemical relationships and formation processes.

Contribution

It offers a detailed comparison of chondrite components, supporting the single-reservoir formation model and constraining astrophysical formation theories.

Findings

Chondrules and matrix have complementary major element ratios.

Semarkona is within 11% of solar Mg/Si ratio.

Results support single-reservoir models for chondrule formation.

Abstract

Abundances, apparent sizes, and individual chemical compositions of chondrules, refractory inclusions, other objects and surrounding matrix have been determined for Semarkona (LL3.00) and Renazzo (CR2) using consistent methods and criteria on x-ray element intensity maps. These represent the non-carbonaceous (NC, Semarkona) and carbonaceous chondrite (CC, Renazzo) superclans of chondrite types. We compare object and matrix abundances with similar data for CM, CO, K, and CV chondrites. We assess, pixel-by-pixel, the major element abundance in each object and in the entire matrix. We determine the abundance of "metallic chondrules" in LL chondrites. Chondrules with high Mg/Si and low Fe/Si and matrix carrying opposing ratios complement each other to make whole rocks with near-solar major element ratios in Renazzo. Similar Mg/Si and Fe/Si chondrule-matrix relationships are seen in Semarkona, which is within 11% of solar Mg/Si but significantly Fe-depleted. These results provide a robust constraint in support of single-reservoir models for chondrule formation and accretion, ruling out whole classes of astrophysical models and constraining processes of chondrite component formation and accretion into chondrite parent bodies.